1. Field of the Invention
The present invention relates to a pattern inspection method and a pattern inspection apparatus, and more particularly to pattern inspection method capable of performing a review and analysis without interrupting an inspection operation for fault information with regard to a prescribed pattern, and to an associated pattern inspection apparatus.
2. Description of the Related Art
In the past, in the process of manufacturing a semiconductor device, many processes have been used to form a pattern of a specific shape in a specific member.
In each of these processes, to ensure that the desired pattern satisfies pre-established conditions, it is necessary that a master pattern be precisely formed.
For this reason, whether or not the master pattern is precisely formed greatly affects the quality and performance of the final semiconductor product, and also influences an improvement in yield.
A general example of such a master pattern is in an electron beam exposure method, in which a reticule is used onto which are formed a plurality of patterns used when forming a desired pattern on a wafer, in which precision in the patterns formed on the reticule is important.
The problems involved in an example of a method of inspecting the patterns formed in a reticule are described below.
Specifically, in an LSI manufacturing process (patterning), a reticule is used to form a prescribed pattern on a semiconductor made of silicon or the like. If there is a pattern defect in the reticule itself, the defective pattern will be transferred to a large number of wafers, causing the manufacture of a large number of defective LSI devices, thereby making inspection of the reticule very important.
Visual inspection methods for a reticule used in LSI manufacturing include the die-to-die inspection method, in which the same pattern at different locations on a reticule are compared, and the die-to-database inspection method, in which a comparison is made between a reticule pattern and image data used to form the reticule pattern.
The term die used herein is used to indicate a pattern area including a certain number of patterns as a group used as an unit of a pattern comparison inspection or an a detected image thereof, while the term database used herein refers with respect to an actual pattern image data detected with an optical system, but rather to image data based on coordinate data, such as a reference image synthesized from CAD data or the like, for example.
A reticule inspection apparatus of the past was disclosed, for example, in the Japanese Unexamined Patent Publication (KOKAI) No. 10-185531, in Japanese Patent No. 2776416, and in the Japanese Unexamined Patent Publication (KOKAI) No. 4-365045.
Specifically, a reticule inspection apparatus of the past was generally formed by an XY stage for setting the reticule, an imaging optical system for forming a photoimage of the pattern of the reticule set on the XY stage to serve as a comparison image, an image input section for acquiring a photoimage that is the comparison image from the imaging optical system, a data conversion section that converts image data used in describing the reticule, such as CAD data, to a reference image, an image comparison section for comparing the comparison photoimage with the reference image so as to detect defects in the pattern, and a controller to perform overall control of the apparatus.
A reticule inspection apparatus of the past moved the stage onto which was set a reticule, and acquired one frame of pattern on the reticule using an imaging optical system and image input section, and sent the acquired image to the image comparison section.
The reference image is converted beforehand by the data conversion section to a reference image from, for example, CAD data, and is sent to the image comparison section in synchronization with the image.
At the image comparison section, a comparison is made between the image and the reference image, so as to detect defects.
A frame used in the above-noted prior art example is the unit of image that can be processed by the image comparison section at one time.
Compared to the time for acquisition of an image by the imaging optics system and image input section, the time for transfer from the image input section to the image comparison section, the time for conversion of the image data, and the time for image processing to detect defects are significantly long, so that in a reticule inspection apparatus of the past, even if the next frame of image is acquired by the image input section, unless the series of processing for defect detection in the previous frame is completed, it is not possible to transfer the next frame of image, thereby resulting in a waiting time.
For this reason, the stage movement speed is made slow, thereby delaying the image acquisition time so as to achieve adjustment of timing, but this results in the lengthening of the overall inspection time.
In the above-noted the Japanese Unexamined Patent Publication (KOKAI) No. 10-185531, in the above-noted technical constitution, in order to improve defect detection precision and shorten detection time, a method of dividing a laser beam is used. In the above-noted Japanese Patent No. 2776416, for the same purpose, a simulation means is adopted, and a comparison is made between the results of the simulation and an actually measured pattern image. In the Japanese Unexamined Patent Publication (KOKAI) No. 4-365045, the method adopted is that of using CAD data as reference data, and the above-noted problems remain basically unsolved.
Given the above, the inventors, in the Japanese Unexamined Patent Publication (KOKAI) No. 10-115049, proposed an improved technology as shown in FIG. 7.
Specifically, when performing pattern inspection, inspection in each region is done by first moving an XY stage 3, onto which is set a reticule 9, to an inspection staring position.
Next, the XY stage 3 is fed in the X direction at a constant speed, as a laser scanning optical system scans in the Y direction each time a laser interferometer detects movement by a constant pitch, the transmitted light being detected by a transmitted light detection section 5, and an optical image input distribution section 6 acquiring a two-dimensional image for each frame.
The acquired optical images are synthesized by image comparison sections 71 to 74 for each frame separately, a comparison is made with a reference image, and defect detection is performed. The term frame used herein refers to the image that can be processed at one time by the image comparison section.
In FIG. 7, the reference numeral 1 denotes a scanning controller, and 2 is an overall controller.
In a method of inspection employed with this type of inspection apparatus, division is made into a plurality of overlapping inspection regions with their long dimensions in the X direction, for example, as shown in FIG. 3, scanning being sequentially performed for each region, after which the defects for each region are combined so as to perform defect detection for the overall reticule.
In the above-noted method, although the problems with the prior art are significantly improved upon, there is still the problem in the case in which a large number of defects are detected in each inspection region, in which case a large amount of time is required by the controller in order to extract defect information from each channel, thereby causing a waiting time to occur before image acquisition for the next inspection region, which meant that the problem of the overall inspection requiring a long time remained not fully solved.
Additionally, in the case in which defects detected during inspection are reviewed in real time, it is necessary to interrupt inspection in order to search for defect images stored in the controller, thereby leaving the problem that the overall inspection time is long.
Accordingly, it is an object of the present invention, in order to improve on the above-noted drawbacks in the prior art, to provide a pattern inspection method whereby, even if a large number of defects are detected during inspection and a review is to be made of defects in real time, it is possible to continue inspection without interruption, thereby providing an improvement in productivity. It is a further object of the present invention to provide a pattern inspection apparatus associated with the above-noted pattern inspection method.
In order to achieve the above-noted objects, the present invention has the following basic technical constitution.
Specifically, a first aspect of the present invention is a pattern inspection method which, in detecting defects in various patterns used in manufacturing a semiconductor device, has a first step of dividing a pattern under inspection into a pre-established number of regions and sequentially acquiring, via an optical means, image information with regard to partial patterns under inspection in each region, a second step of storing the image information with regard to the partial pattern under inspection acquired by the first step into a comparison pattern image information storage means provided in each of a pre-established plurality of image comparison sections, respectively, a third step of, in image processing means provided in each individual image comparison section, performing a comparison between the image information with regard to the partial patterns under inspection stored in the comparison pattern image information storage means and reference pattern image information (reference image information) corresponding to the partial pattern under inspection in the divided regions, which is stored beforehand in a reference pattern image information storage means provided in the image comparison sections, a fourth step of, in the case in which defect information exists with regard to a partial pattern under inspection, storing the defect information into a defect information storage means provided in a review controller, and a fifth step of outputting the defect information with regard to partial patterns under inspection for a prescribed divided region stored in the defect information storage means in a prescribed format or at a prescribed time.
A second aspect of the present invention is a pattern inspection apparatus for detecting defects in various patterns used in manufacturing a semiconductor device, this apparatus having a moving holding means for holding and moving in a prescribed direction a pattern holding member that holds a pattern under inspection, an optical means for generating pattern image data of a partial pattern under test from a pattern under test held by the moving holding means for every predetermined divided regions of the pattern under inspection, a plurality of image comparison sections that compare the individual partial patterns under inspection of the pattern under inspection with prescribed reference pattern image information, and make a judgment as to whether or not a defect exists in the partial patterns under inspection, each the image comparison sections minimally comprising a comparison pattern image information storage means which stores comparison pattern image data for a partial pattern under inspection corresponding to a specific inspection divided region, a reference pattern image information storage means which stores reference pattern image data corresponding to each of the partial patterns under inspection, and an image processing means that performs a comparison between the comparison pattern image data stored in the comparison pattern image information storage means and the reference pattern image data stored in the reference pattern image information storage means, and makes a judgment as to whether or not there is a defect in the pattern under inspection, a defect information accumulation means, which sequentially stores defect information in a prescribed partial pattern under inspection output by the image processing means in each the image comparison sections, a reviewing means, which outputs defect information with regard to each of the partial patterns under inspection stored in the defect information accumulation means with a prescribed format or at a prescribed time, and a central control means which performs appropriate overall control of the above-noted means.
By adopting the above-noted technical constitutions, even in the case in which a large number of defects are detected or even in the case in which defect reviewing is done in real time, a pattern inspection apparatus and pattern inspection method according to the present invention, by a simple addition to a precision visual reticule inspection apparatus for LSI device manufacturing, enable to perform continuous, uninterrupted inspection, thereby improving the productivity of the pattern inspection process.
Specifically, the review controller performs real-time collection, accumulation, and editing of defect information (including defect images) from each image comparison section, using dedicated lines, and searches and displays defect images on demand.
By doing the above in the present invention, because the review controller performs independent collection, accumulation, and editing of defect information detected for each channel, even if many defects are detected or if review is performed during the inspection process, it is not necessary to interrupt the inspection operation, thereby shortening the inspection time.
Additionally, because there is an existing database of past defect information in the review controller, it is possible to perform analysis of process problems and classification of defects caused by exposuring simulation.